CHMY 121: Exam 4
In the endothermic reaction, 2A(g)+B(s)⇌C(g), what will shift the equilibrium to the right?
-adding more A -removing some C -decreasing the volume -increasing the temperature
In the exothermic reaction, X(g)⇌Y(g)+Z(s), what will shift the equilibrium to the left?
-adding more Y -removing some X -increasing the temperature
What is the gas constant?
0.0821 (L)(atm)/(mol)(K)
How many grams of O2 are contained in a 25.0 L sample at 5.20 atm and 28.0°C?
168 g
How many mmHg are in 1 atm?
760 mmHg
What is the ideal gas law?
PV=nRT
If n + T stay the same, but P doubles, what happens to V?
V is halved; (P1V1=P2V2)
What would describe ideal gas according to the kinetic-molecular theory of gases?
Volume occupied by gas molecules themselves is not comparable to the volume between molecules.
If we treat gases as independent, non-interacting molecules, what do we have?
an ideal gas
When the concentration of SO2(g) is increased to 1.48 M, the ratio of products to reactants is 1.4. The equilibrium constant for the reaction is 14. In which direction will the reaction shift to regain equilibrium?
toward the products
T and P are proportional, true or false?
true
6CO2(g)+6H2O(l)⇌C6H12O6(s)+6O2(g) Which is true when the photosynthesis reaction reaches equilibrium?
-The rate of formation of O2 is equal to the rate of formation of CO2. -The concentrations of CO2 and O2 will not change.
Consider a gas in a sealed, rigid container. What will increase if more gas is pumped into the container at constant temperature?
-the pressure of the gas -the number of gas particles -the collision frequency of the gas particles
Consider a gas in a sealed, rigid container. What will increase if the temperature of the gas is increased?
-the speed of the gas particles -the kinetic energy of the gas particles -the collision force of the gas particles -the pressure of the gas
What are the characteristics of an ideal gas?
-the speed/kinetic energy is determined by temp (k) -the collisions are elastic -no interactions/intermolecular forces -molecules move in straight paths until collision -all gases behave the same -the gas molecules are small, occupy no space -the molecules are free to move in container -pressure depends on frequency + force of collisions
For the reaction 2SO2 (g) + O2 (g) ⇌ 2SO3 (g) K = 4.62 at 450 K. The concentrations at equilibrium are found to be: [SO3] = 0.360 mol/L, [O2] = 0.00945 mol/L. What is the equilibrium concentration for SO2?
1.72 mol/L
A balloon at constant temperature and pressure, containing 3.75 mole of ideal gas, occupies 24.5 L volume. Upon the addition of more gas into the balloon, the volume expanded to 42.0 L. How many moles of gas were added?
2.68 mol
A reaction is exothermic when delta H is...
negative
A reaction is endothermic when delta H is...
positive
Increasing the temperature in an endothermic reaction, shifts the equilibrium to the...
right
High-pressure liquid chromatography (HPLC) is a method used in chemistry and biochemistry to purify chemical substances. The pressures used in this procedure range from around 500 kilopascals (500,000 Pa) to about 60,000 kPa (60,000,000 Pa). It is often convenient to know the pressure in torr. If an HPLC procedure is running at a pressure of 4.62×108 Pa , what is its running pressure in torr?
3.47×106 torr
For the reaction H2(g)+I2(g) ⇌ 2HI(g) the equilibrium concentrations at 25∘C are[H2]= 0.0510mol/L, [I2]= 0.174mol/L, and [HI]= 0.507mol/L. What is the value of K at 25 ∘C?
K = 29.0
2SO2(g) +O2(g)⇌2SO3(g) At equilibrium, the molar concentrations for reactants and products are found to be [SO2]=0.48M, [O2]=0.40M, and [SO3]=1.12M. What is the equilibrium constant (Kc) for this reaction?
Kc = 14
The molar concentrations for the reactants and products at equilibrium are found to be [HCl]=0.80 M, [O2]=0.20 M, [Cl2]=3.0 M, and [H2O]=3.0 M. What is the value of the equilibrium constant for this reaction? 4HCl(g)+O2(g)⇌2Cl2(g)+2H2O(g)
Kc = 990
N2+O2⇌2NO at 2000 ∘C are [N2]=0.25M; [O2]=1.2M; [NO]=0.011M. What is the value of Keq for this reaction?
Keq = 4.0⋅10^−4
What units is Keq in?
Keq is unitless
If an equilibrium involves solubility, we do we call it instead of Keq?
Ksp
What amount of pressure would it take to compress 350. L of helium gas initially at 1.00 atm into a 2.00 L tank at constant temperature?
P = 175 atm
A sample of ideal gas is in a sealed container. The pressure of the gas is 195 torr , and the temperature is 35 ∘C . If the temperature changes to 66 ∘C with no change in volume or amount of gas, what is the new pressure, P2, of the gas inside the container?
P2 = 215 torr
What types of solutions have essentially no change in their concentrations?
Pure liquids and solids
Does adding a catalyst have any effect on equilibrium?
no
What does n represent in a equation?
number of moles in a gas
What happens to pressure when temperature is increased?
pressure increases
What happens to pressure when the amount of gas is increased?
pressure increases
What happens when to pressure when volume decreases?
pressure increases
Exothermic reactions produce heat as a...
product
At equilibrium, this reaction (Kc=990) favors the...
products
If the Keq is bigger then it will favor the...
products
When you increase the reactants, or decrease the products, you make more...
products
Endothermic reactions produce heats as a...
reactant
If the Keq is smaller then it will favor the...
reactants
When you increase the products or decrease the reactants, you make more....
reactants
What is hetero equilibra?
reactants and products in different phases
Why is Keq important?
shows to what degree the reaction favors products or reactants
In the endothermic reaction, 2A(g)+B(s)⇌C(g), what will cause no change in the equilibrium?
the addition/removal of B, because it is a solid
HSO4− is the conjugate _____ of H2SO4 and the conjugate _____ of SO42−.
base/acid
n and P are not inversely proportional, true or false?
false, they are proportional
Why is acetic acid a weak acid in water?
it only slightly dissociates into ions
Increasing the temperature in an exothermic reaction, shifts the equilibrium to the...
left
decreased volume/increased pressure shift the equilibrium toward...
the fewest number of molecules in the GAS phase
What happens when a reaction reaches equilibrium?
two competing reactions continue to occur simultaneously at equal rates
What does Le Châtelier's principle state?
when a chemical system at equilibrium is disturbed (stress is added), the system shifts in a direction that minimizes the disturbance (stress). -example: panic attack
In the exothermic reaction, X(g)⇌Y(g)+Z(s), what will cause no shift in the equilibrium?
-adding more Z -decreasing the volume (bc Z is a solid)
In the endothermic reaction, 2A(g)+B(s)⇌C(g), what will shift the equilibrium to the left?
-removing some A -adding more C -increasing the volume -decreasing the temperature
In the exothermic reaction, X(g)⇌Y(g)+Z(s), what will shift the equilibrium to the right?
-removing some Y -adding more X
Chlorine gas is widely used to purify municipal water supplies and to treat swimming pool waters. Suppose that the volume of a particular sample of Cl2 is 718 mL at 675 mmHg and 48°C, at what temperature (in °C) will the volume be 2.00 L if the pressure is 159 kPa?
1308°C
2SO2(g)+O2(g)⇌2SO3(g) What is a true statement about this reaction?
2SO2(g)+O2(g)⇌2SO3(g) -When SO2 is mixed with O2 in a container, the initial rate of the forward reaction (production of SO3) is faster than the initial rate of the reverse reaction (production of SO2). -At equilibrium, the concentration of SO2 will no longer be changing.
Calculate the equilibrium constant for the reaction below if a tank was found to contain 0.106 M O2, 0.00652 M SO3, and 0.00129 M SO2 2 SO3 (g) ⇌ 2 SO2 (g) + O2 (g)
4.15 × 10^-3
If a 0.614 g sample of a gas maintains a pressure of 238 mm Hg when contained in a 1.0 L flask at 0.0°C, what is molar mass of the gas?
44 g/mol
Why don't concentrations change at equilibrium?
Concentrations do not change at equilibrium because all species are being produced at the same rate as they are being consumed.
Using the same sample of gas (P1 = 195 torr , T1 = 35 ∘C ), we wish to change the pressure to 1950 torr with no accompanying change in volume or amount of gas. What temperature T2, in Celsius, is needed to reach this pressure?
T2 = 2810 ∘C
What Celsius temperature, T2, is required to change the volume of the gas sample in Part A (T1 = 35 ∘C , V1= 1.75×103 L ) to a volume of 3.50×103 L ? Assume no change in pressure or the amount of gas in the balloon.
T2 = 343 ∘C
A weather balloon is filled with helium to a volume of 335 L at 16 ∘C and 761 mmHg . The balloon ascends to an altitude where the pressure is 476 mmHg and the temperature is -27 ∘C. What is the volume of the balloon at this altitude?
V = 456 L
A balloon filled with 2.00 L of helium initially at 2.15 atm of pressure rises into the atmosphere. When the surrounding pressure reaches 450. mmHg, the balloon will burst. If 1 atm = 760. mmHg, what volume will the balloon occupy in the instant before it bursts?
V = 7.26 L
A sample of gas in a balloon has an initial temperature of 35 ∘C and a volume of 1.75×103 L . If the temperature changes to 70. ∘C , and there is no change of pressure or amount of gas, what is the new volume, V2, of the gas?
V2 = 1950 L
If you have more [H+] and less [OH-], do you have an acid or a base?
acid
Identify the acid, base, conjugate base, and conjugate acid: H2CO3 + H2O -> <- (HCO3-) + (H3O+)
acid: H2CO3 conjugate base: HCO3- base: H2O conjugate acid: H3O+
Identify the acid, base, conjugate base, and conjugate acid: HCO3- + H2O -> <- (CO3^2-) + (H3O+)
acid: HCO3- conjugate base: CO3^2- base: H2O conjugate acid: H3O+
What are the three major factors that will add stress to a system in equilibrium?
concentration, volume, and temperature
